\section{Conclusion and Future Work}


This paper presented a practical approach (and its
tool implementation, called \ourtool) for enforcing
user privacy on mobile platforms. Our experimental
results show that \ourtool is able to precisely enforce the specified privacy policy with very little runtime overhead.

We consider \ourtool as one step towards improving the
user privacy on mobile platforms. We would
concentrate on the following directions in the future.

\begin{itemize}

\item \textbf{User study.}		
We plan a user study to evaluate \ourtool's		
usefulness to end-users. Especially the third practical use scenario, in which the users will be given the ability to block or allow sensitive information flows when they occur. 

\item \textbf{Implicit Information Flow.} A recent paper~\cite{haichen} has shown the effectiveness of static analysis assisted approaches in dynamically profiling how sensor data are implicitly used in mobile apps (such as step counters and geo fencing apps). They leveraged static analysis to identify the effect scope of the conditionals (if else blocks) and apply those information during runtime to help dynamic information flow tracking. Since \ourtool also uses static analysis to assist dynamic enforcement, it would be interesting to explore if their approach can be applied to precisely track implicit sensitive information flows.

\item \textbf{Integrating with symbolic analysis and model checking.}		
\ourtool uses dynamic enforcement to ensure user privacy.
Despite its usefulness, dynamic enforcement cannot prove
the absence of user privacy leakage. To alleviate this problem,		
we plan to integrate \ourtool with existing symbolic		
analyses or model checking techniques to statically
verify the user privacy leakage.
%its results more complete.


\end{itemize}
